Hemoglobin plays a role to carry oxygen in blood. The concentration of hemoglobin in blood fluctuates in accordance with the duration and contraction of vessels, and therefore it is known that the duration and contraction of vessels can be detected by measuring the concentration of hemoglobin.
Thus, an organism measuring method is known for simply and non-invasively measuring the inside of an organism using light by employing the fact that the concentration of hemoglobin corresponds to the oxygen metabolizing function inside an organism. The concentration of hemoglobin can be found from the amount of light that is gained when transmitted through an organism when the organism is irradiated with light of which the wavelength ranges from that of visible light to near infrared rays.
Furthermore, hemoglobin combines with oxygen so as to be oxyhemoglobin (hereinafter referred to as oxyHb), and conversely detaches from oxygen so as to be deoxyhemoglobin (hereinafter referred to as deoxyHb). It is also known that within a brain, oxygen is supplied to a portion that is activated through a blood flow redistributing effect, and the concentration of oxyhemoglobin that has combined with oxygen increases. Therefore, the measurement of the concentration of oxyhemoglobin can be applied to the observation of brain activities. Oxyhemoglobin and deoxyhemoglobin have different absorption spectra for light ranging from visible light to near infrared rays, and therefore, the concentration of oxyhemoglobin and the concentration of deoxyhemoglobin can be found by using two types of near infrared rays having different wavelengths, for example.
Thus, an organism optical measurement device having a light transmitting probe and a light receiving probe has been developed in order to non-invasively measure brain activities. In the organism optical measurement device, the light transmitting probe disposed on the surface of the head of a subject irradiates the brain with near infrared rays, and at the same time, the light receiving probe disposed on the surface of the head detects the amount of near infrared rays emitted from the brain. Near infrared rays transmit through the scalp tissue and the bone tissue and are absorbed by the oxyhemoglobin and deoxyhemoglobin in blood. Therefore, the light transmitting probe and the light receiving probe can be used to find chronological changes in the concentration of oxyhemoglobin, the concentration of deoxyhemoglobin, and the total concentration of hemoglobin that can be calculated from these in the measured portion in the brain as the measurement data. FIG. 6 is a graph showing an example of the measurement data. Here, the longitudinal axis shows the concentration and the lateral axis shows the time.
Here, the relationship between the measured portion in the brain and the distance (channel) between the light transmitting probe and the light receiving probe is described. FIG. 7(a) is a cross-sectional diagram showing the relationship between the measured portion in the brain and the pair of probes, light transmitting probe and light receiving probe, and FIG. 7(b) is a plan diagram of FIG. 7(a).
The light transmitting probe 12 is pressed against the light transmitting point T on the surface of the head of a subject, and at the same time, the light receiving probe 13 is pressed against the light receiving point R on the surface of the head of the subject. Thus, light is irradiated from the light transmitting probe 12, and at the same time, the light receiving probe 13 detects the light emitted from the surface of the head. At this time, the light that has passed through the banana-shaped region (measurement region) after being irradiated through the light transmitting point T on the surface of the head reaches the light receiving point R on the surface of the head. As a result, information gained from the amount of light received particularly by the portion S of the subject (concentration of oxyhemoglobin, concentration of deoxy hemoglobin, and total concentration of hemoglobin calculated from these) can be found in the measurement region where the portion S is located at a depth L/2, which is half of the shortest length of the line connecting the light transmitting point T and the light receiving point R along the surface of the head of the subject from the middle point M of the shortest length L of the line connecting the light transmitting point T and the light receiving point R along the surface of the head of the subject.
In recent years, organism optical measurement devices that can be applied in the medical field, such as brain function diagnosis and circulatory disorder diagnosis, measuring the concentration of hemoglobin in the measured portion in the brain relating to the brain functions, such as motion, sense and thought, have been developed. Such organism optical measurement devices have been applied to near infrared spectrometric analyzers, for example (see Japanese Unexamined Patent Publication 2006-109964).
In near infrared spectrometric analyzers, a holder is used so that a number of light transmitting probes and a number of light receiving probes can be made to make close contact with the surface of the head of a subject in a predetermined arrangement. An example of this holder is a mold holder that has been molded in bowl form so as to fit on the surface of a head. A number of through holes are provided in the mold holder, and the light transmitting probes and the light receiving probes are inserted into these through holes so that the channels become constant and information can be gained from the amount of light received at a specific depth from the surface of the head.
FIG. 8 is a plan diagram showing the positional relationships of 12 light transmitting probes and 12 light receiving probes in a near infrared spectrometric analyzer as described above. Light transmitting probes 12a to 12l and light receiving probes 13a to 13l are aligned so as to alternate in the diagonal directions. Here, light irradiated from the light transmitting probes 12a to 12l can be detected by the light receiving probes 13a to 13l, which are not adjacent to the light transmitting probes 12a to 12l, but here, only the adjacent light receiving probes 13a to 13l can detect the light in order to make the description simple. Thus, 36 pieces of information (measurement data) can be gained from the amount of light received.
Here, the channels are generally 30 mm, and in the case where the channels are 30 mm, information should be able to be gained from the amount of received light at a depth of 15 mm to 20 mm from the middle point of the channels as described above. That is to say, the points at a depth of 15 mm to 20 mm from the surface of the head mostly correspond to the portions on the surface of the brain, and thus, information (measurement data) on the brain activities can be gained from the amount of received light. Thus, the measurement data on the brain activities gained in a near infrared spectrometric analyzer is displayed as an image so that doctors and the like can observe. FIG. 9 is a diagram showing an example of a monitor screen where a conventional organism optical measurement device displays 36 pieces of measurement data.
The monitor screen displays 36 pieces of measurement data #1 to #36. At this time, each piece of measurement data gained when a light receiving probe 13 detects light irradiated from a light transmitting probe 12 is aligned for the display at the middle point of the shortest line connecting the light transmitting probe 12 and the light receiving probe 13 in the plan diagram in FIG. 8. For example, the piece of measurement data #1 when the light receiving probe 13a detects the light irradiated from the light transmitting probe 12a is aligned in the upper left, the piece of measurement data #2 when the light receiving probe 13d detects the light irradiated from the light transmitting probe 12a is aligned beneath the piece of measurement data #1, and the piece of measurement data #7 when the light receiving probe 13a detects the light irradiated from the light transmitting probe 12b is aligned to the right of the piece of measurement data #1, and thus the 36 pieces of measurement data #1 to #36 are aligned.
Though mold holders are used to make 12 light transmitting probes 12 and 12 light receiving probes 13 make close contact with the surface of the head as described above, some light transmitting probes 12 or light receiving probes 13 may not make close contact with the surface of the bead due to hair on the surface of the head. As a result, in some cases, some of the 36 pieces of measurement data #1 to #36 are inaccurate pieces of measurement data. At this time, it cannot easily be determined whether or not a piece of measurement data is inaccurate even in the case where there seems to be an inaccurate piece of measurement data or it is perceived that a certain piece of measurement data is inaccurate.
It is also difficult to find from which measured portion in the brain a certain piece of measurement data is gained because 36 pieces of measurement data #1 to #36 are simply aligned as shown in FIG. 9.